With state-of-the-art conventional carbon electrodes a pair of longitudinally extending vertically positioned electrode sections are coupled by means of a threaded graphite nipple which is threaded into correspondingly threaded opposed sockets of the electrode sections by relative rotation of the electrode sections, with the result that the respective opposing butt faces of the vertical electrode sections are brought into abutting contact. As an electrode section is consumed in the course of furnace operation, a new electrode section is tandemly coupled in the same manner so that furnace operation can proceed continuously. That is, as the lower end of the column is consumed in the furnace, the entire column is lowered to maintain the operation and electrode sections are joined to the top of the column to replenish the consumed columns. However, there is occasional loosening of the threadably engaged joint by rotation of an electrode section in a direction opposite to its threading direction which can lead to increased electrical resistance and also to mechanical failure, i.e. breakage of a threaded nipple joint which requires the interruption of electric furnace operation.
An early prior art effort to address this problem with respect to horizontally positioned carbon electrode sections is disclosed in U.S. Pat. No. 1,572,534--Hinckley which describes a variety of blade shaped metal implements which are forced into the electrode joint and act as a key to prevent loosening of the joint. Due to the temperatures experienced in modern electric arc furnaces, a metal key would melt and be ineffective as the electrode joint approached the high temperature electrode arc from above. Also, U.S. Pat. No. 4,813,805--Dagata discloses the use of a peg extending between upper and lower electrode sections which is held in place by coked pitch.